Printing apparatus and printing method

ABSTRACT

In a printing chip overlapping area being an area in which a first printing chip and a second printing chip overlap with each other when viewed from a second direction, ink is discharged so that a first overlapping area and a second overlapping area at least partially do not overlap with each other when viewed from the second direction. In the first overlapping area, a nozzle usage ratio of a first nozzle row and a nozzle usage ratio of a third nozzle row are neither 0% nor 100%. In the second overlapping area, a nozzle usage ratio of a second nozzle row and a nozzle usage ratio of a fourth nozzle row are neither 0% nor 100%.

BACKGROUND I. Technical Field

The invention relates to a printing apparatus.

2. Related Art

Recent years, as a printing apparatus, an ink jet-type printer includingprinting chips has been used. The printing chips are obtained bychipping an ink discharge mechanism including a piezoelectric element,an ink chamber, and a nozzle through application of a semiconductorprocessing technique. Each printing chip includes a plurality of nozzlerows arrayed along a conveyance direction of a printing medium. In astructure in which the plurality of printing chips are mounted on oneprinting head, ends of the plurality of printing chips adjacent to eachother in a main scanning direction are arranged to overlap with eachother when viewed from the main scanning direction in some cases. In anarea in which the ends of the printing chips overlap with each other,ink is discharged from nozzle rows of the printing chips so that anozzle usage ratio between the nozzle rows arranged on one printing chipand the nozzle rows arranged on another printing chip is 100%. In thismanner, a raster of the area is formed (for example, JP-A-2015-150828).

However, in JP-A-2015-150828, in the area in which the ends of theprinting chips overlap with each other (hereinafter, referred to as“printing chip overlapping area”), the nozzle rows on the same printingchip are arranged substantially at the same positions as each other whenviewed from the main scanning direction. Thus, when landing positions ofink droplets are deviated, such landing position deviation issimultaneously caused to the plurality of nozzle rows in the printingchip overlapping area. Accordingly, uneven density may possibly notablyappear in a printing image. Further, in JP-A-2015-150828, the nozzlerows of each printing chip discharge the same color ink as each other. Anozzle group discharging ink simultaneously is positioned in each nozzlerow in an area (hereinafter, referred to as “ink discharge area”). Suchink discharge areas are substantially at the same positions as eachother when viewed from the main scanning direction. With this structure,also in a case where landing position deviation of ink droplets iscaused due to variation of an ink discharge amount and an ink dischargespeed and the like caused by a drive frequency difference among thenozzles, the landing position deviation is caused in the ink dischargeareas at the same time. Accordingly, uneven density may further benoticeable in a printing image. Therefore, a technology for suppressingdegradation of printing image quality in the printing chip overlappingareas in the printing image is desired.

SUMMARY

The invention has been made to address at least some of theabove-described issues and can be achieved as the following embodiments.

(1) According to an exemplary embodiment of the invention, a printingapparatus is provided. The printing apparatus is a printing apparatusfor performing printing on a medium, the printing apparatus including aprinting head including a first printing chip and a second printingchip, which are arranged to at least partially overlap with each otherwhen viewed from a second direction, the first printing chip including afirst nozzle row and a second nozzle row, which are away from each otherin the second direction intersecting a first direction, the first nozzlerow and the second nozzle row including a plurality of nozzles arrayedin the first direction for discharging ink onto the medium, the secondprinting chip including a third nozzle row and a fourth nozzle row,which are away from each other in the second direction, the third nozzlerow and the fourth nozzle row including a plurality of nozzles arrayedin the first direction for discharging the ink onto the medium, aconveyance unit configured to convey the medium relatively to theprinting head, and a printing control unit configured to cause theprinting head to discharge the ink onto the medium, based on a nozzleusage ratio being a ratio of the ink discharged from each of theplurality of nozzles. The first nozzle row and the third nozzle row areconfigured to discharge the ink of the same color, the second nozzle rowand the fourth nozzle row are configured to discharge the ink of thesame color, and the printing control unit is configured to cause the inkto be discharged so that a first overlapping area and a secondoverlapping area are at least partially prevented from overlapping witheach other when viewed from the second direction in a printing chipoverlapping area, the first overlapping area being an area in which thenozzle usage ratio of the first nozzle row and the nozzle usage ratio ofthe third nozzle row are not 0% or 100%, the second overlapping areabeing an area in which the nozzle usage ratio of the second nozzle rowand the nozzle usage ratio of the fourth nozzle row are not 0% or 100%,and the printing chip overlapping area being an area in which the firstprinting chip and the second printing chip overlap with each other whenviewed from the second direction.

With the printing apparatus according to the above-mentioned aspect, inthe printing chip overlapping area being the area in which the firstprinting chip and the second printing chip overlap with each other whenviewed from the second direction, the ink is discharged so that thefirst overlapping area being the area in which the nozzle usage ratio ofthe first nozzle row and the nozzle usage ratio of the third nozzle roware neither 0% nor 100% and the second overlapping area being the areain which the nozzle usage ratio of the second nozzle row and the nozzleusage ratio of the fourth nozzle row are neither 0% nor 100% at leastpartially do not overlap with each other when viewed from the seconddirection. Thus, in a case where landing position deviation of inkdroplets is caused both in the first overlapping area and the secondoverlapping area, the areas in which landing position deviation iscaused in the second direction are dispersed so that uneven density isprevented from appearing in an overlapping manner in the seconddirection in the printing image. In this manner, degradation of theprinting image quality in the printing chip overlapping area can besuppressed.

(2) In the printing apparatus according to the above-mentioned aspect,the printing control unit may be configured to, in the printing chipoverlapping area, cause the ink to be discharged so that the firstoverlapping area and the second overlapping area are prevented fromoverlapping with each other when viewed from the second direction. Withthe printing apparatus according to the above-mentioned aspect, in theprinting chip overlapping area, the ink is discharged so that the firstoverlapping area and the second overlapping are do not overlap with eachother in the second direction. Thus, in a case where landing positiondeviation of ink droplets is caused both in the first overlapping areaand the second overlapping area, the areas in which landing positiondeviation is caused in the second direction do not overlap with eachother so that uneven density is prevented from appearing in anoverlapping manner in the second direction in the printing image. Inthis manner, degradation of the printing image quality in the printingchip overlapping area can be suppressed.

(3) The printing apparatus according to the above-mentioned aspect maybe configured such that the printing head includes two or more printingchips including the first printing chip and the second printing chip,the first nozzle row and the third nozzle row are configured todischarge ink of black, the second nozzle row and the fourth nozzle roware configured to discharge ink of yellow, the two or more printingchips further include a fifth nozzle row and a sixth nozzle row beingdifferent from the first nozzle row to the fourth nozzle row, in which aplurality of nozzles for discharging ink of the same color other thanblack and yellow are arrayed in the first direction, the fifth nozzlerow and the sixth nozzle row are arranged away from each other in thesecond direction, and the printing control unit is configured to causethe ink to be discharged so that the first overlapping area and thesecond overlapping area at least partially overlap with each other whenviewed from the second direction in the printing chip overlapping area.

With the printing apparatus according to the above-mentioned aspect, inthe printing chip overlapping area, the ink is discharged so that thefirst overlapping area and the second overlapping area at leastpartially overlap with each other when viewed from the second direction.Thus, as compared to the configuration in which the ink is discharged sothat the first overlapping area and the second overlapping are do notoverlap with each other when viewed from the second direction, theoverlapping areas of the colors other than black and yellow can bearranged at the positions away from the first overlapping area and thesecond overlapping area in the first direction. Further, in a case whereink of a plurality of colors other than black and yellow is used, therecan be secured areas (nozzle groups) in which overlapping areas ofcolors other than black and yellow do not overlap with each other whenviewed from the second direction. Additionally, the printing apparatuscan be reduced in size.

(4) In the printing apparatus according to the above-mentioned aspect,the printing control unit may cause the ink to be discharged so that thefirst overlapping area and the second overlapping area completelyoverlap with each other when viewed from the second direction. With theprinting apparatus according to the above-mentioned aspect, the ink isdischarged so that the first overlapping area and the second overlappingarea completely overlap with each other when viewed from the seconddirection. Thus, as compared to the configuration in which the ink isdischarged so that the first overlapping area and the second overlappingarea overlap with each other when viewed from the second direction, inthe printing chip overlapping area, the overlapping areas of the samecolor other than black and yellow can be arranged away from each otherin the first direction.

The invention may be achieved in various embodiments. For example, theinvention may be achieved in embodiments including a printing method inthe printing device, a computer program for achieving the printingmethod, and a recording medium for storing the computer program.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a block diagram illustrating a schematic configuration of aprinting apparatus according to an exemplary embodiment of theinvention.

FIG. 2 is an explanatory view illustrating a detailed configuration of aprinting head.

FIG. 3 is an explanatory view illustrating a configuration of nozzlerows in a printing chip overlap area and a nozzle usage ratio thereof.

FIG. 4 is a flowchart illustrating a process procedure of printingprocessing.

FIG. 5 is an explanatory view illustrating a printing chip overlappingarea in a Second Exemplary Embodiment.

FIG. 6 is an explanatory view illustrating a nozzle usage ratio ofnozzles in the printing chip overlapping area in the Second ExemplaryEmbodiment.

FIG. 7 is an explanatory view illustrating a nozzle usage ratio ofnozzles in the printing chip overlapping area in the Second ExemplaryEmbodiment.

FIG. 8 is an explanatory view illustrating a nozzle usage ratio ofnozzles in the printing chip overlapping area in the Second ExemplaryEmbodiment.

FIG. 9 is an explanatory view illustrating a nozzle usage ratio ofnozzles in the printing chip overlapping area in the Second ExemplaryEmbodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS A. First Exemplary Embodiment

A1. Device Configuration:

FIG. 1 is a block diagram illustrating a schematic configuration of aprinting apparatus 100 according to an exemplary embodiment of theinvention. The printing apparatus 100 is a serial ink jet-type printer.The printing apparatus 100 is configured to print an image, a character,and the like by converting image data input from a printing controldevice 10 to printing data, causing a plurality of nozzles to dischargeinks onto a medium P based on the printing data to form dots on themedium P. Specifically, in the printing apparatus 100, inks of three ormore colors including black and yellow are discharged. In the FirstExemplary Embodiment, in the printing apparatus 100, inks of four colorsof cyan (C), magenta (M), yellow (Y), and black (K) are discharged. Inthe First Exemplary Embodiment, the medium P is a printing paper sheet.Note that, the medium P is not limited to the printing paper sheet, andany medium on which an image or the like can be formed with ink dots maybe used.

The printing apparatus 100 includes a control unit 200, a medium feedingunit 310, a medium conveyance unit 320, a carriage conveyance unit 330,a carriage 500, and a printing head 400.

The control unit 200 is configured to perform overall control of theprinting apparatus 100. The control unit 200 is formed of amicrocomputer, and includes a CPU 220, a memory 230, and an input/outputinterface (input/output I/F) 210. The CPU 220, the memory 230, and theinput/output interface 210 are connected to an internal bus, and areformed to be capable of communicating with each other.

The CPU 220 is configured to execute a control program (not illustrated)stored in the memory 230 in advance to function as a printing controlunit 221. The printing control unit 221 is configured to performprocessing for generating printing data from image data input from theprinting control device 10 and integrated control processing forprinting based on the printing data. Specifically, the printing controlunit 221 is configured to convert a resolution of the image data inputfrom the printing control device 10 to a printing resolution to obtainthe image data expressed with gradation values of the ink colors C, M,Y, and K. Further, the printing control unit 221 is configured toconvert the image data of each ink color to two-level gradation valuesindicating presence or absence of dots of each ink color, that is, atwo-level gradation value indicating dot presence (255) and dot absence(0). The printing control unit 221 is configured to rasterize the dataindicating presence or absence of dots of each ink color C, M, Y, or Kon the medium P, and generate the printing data containing a command forprinting control.

Further, based on the printing data, the printing control unit 221 isconfigured to generate a signal for driving nozzle groups provided tothe printing head 400 (hereinafter, referred to as “input signal”), andtransmit the signal to the printing head 400. The printing control unit221 is configured to control the medium feeding unit 310 to controlfeeding of the medium P. The printing control unit 221 is configured tocontrol the medium conveyance unit 320 to convey the medium P. In FIG.1, the medium P is conveyed from upstream to downstream along a subscanning direction Y. The printing control unit 221 is configured tocontrol the carriage conveyance unit 330 to reciprocate the carriage500. In FIG. 1, the carriage 500 is configured to move along a mainscanning direction X. The main scanning direction X is a directionintersecting the sub scanning direction Y, and a direction orthogonal tothe sub scanning direction Y in the First Exemplary Embodiment.

In the memory 230, a first dither mask 231, a second dither mask 232, amask selecting map 233, and a nozzle usage ratio setting map 234 arestored in advance. The first dither mask 231 and the second dither mask232 are dither masks different from each other. In the First ExemplaryEmbodiment, in halftone processing in printing processing, which isdescribed below, dot data of a certain image area (overlapping areadescribed below) in an image area indicated by the image data isgenerated through use of a threshold value set in the first dither mask231, and dot data of a certain image area (single printing chip areadescribed below) in the image area indicated by the image data isgenerated through use of a threshold value set in the second dither mask232. In the mask selecting map 233, a dither mask to use, which isselected between the first dither mask 231 and the second dither mask232, is set in advance with respect to each pixel of the image data. Inthe nozzle usage ratio setting map 234, a nozzle usage ratio for nozzlesis set advance. In the printing processing described below, the printingcontrol unit 221 causes each nozzle to discharge ink based on the nozzleusage ratio. Note that, the nozzle usage ratio is described below indetail.

In the printing apparatus 100, the input/output interface 210 includesvarious interface groups for connection with an external device. As theexternal device, the printing control device 10, a digital still camera(not illustrated), and a smartphone (not illustrated) are exemplified.As the various interface groups, there are exemplified interface groupsfor performing communication through, for example, a Universal SerialBus (USB), Bluetooth (trade name), various wired LANs specified inIEEE802.3 standard, and various wireless LANs specified in IEEE802.11standard. The input/output interface 210 outputs the image data inputfrom the external device to the CPU 220.

The printing control device 10 is configured to be capable ofcommunicating with the printing apparatus 100, and cause the printingapparatus 100 to perform printing by transmitting the image data of anobject to be printed. In the First Exemplary Embodiment, the printingcontrol device 10 is formed of a personal computer. A printer driver isincluded in an operating system to be operated in the printing controldevice 10.

The medium feeding unit 310 includes a paper sheet tray (notillustrated). In response to a control signal from the printing controlunit 221, the medium feeding unit 310 feeds the medium P stored in thepaper sheet tray to downstream in the sub scanning direction Y. Notethat, in place of the paper sheet tray, a roll body around which themedium P is wound, a roll drive motor, and a roll drive wheel may beincluded.

The medium conveyance unit 320 includes a conveyance roller 321. Themedium conveyance unit 320 is configured to drive, in response to acontrol signal from the printing control unit 221, a conveyance roller321 to rotate, to thereby move the medium P fed from the medium feedingunit 310 relatively to the carriage conveyance unit 330. Although notillustrated, sensors such as a feeding detection sensor for detecting aconveyance amount of the medium P and a leading-edge detection sensorfor detecting a leading-edge position of the medium P are provided tothe medium conveyance unit 320. The printing control unit 221 isconfigured to control the medium conveyance unit 320 with reference tosignals from those sensors.

The carriage conveyance unit 330 is configured to reciprocate, inresponse to a control signal from the printing control unit 221, thecarriage 500 in the main scanning direction X. The carriage conveyanceunit 330 includes a carriage guide shaft 331 and a carriage motor (notillustrated). The carriage guide shaft 331 is arranged in the mainscanning direction X, and both ends of carriage guide shaft 331 arefixed to a housing of the printing apparatus 100.

The carriage 500 is mounted to the carriage guide shaft 331 so as to bereciprocable in the main scanning direction X. The carriage conveyanceunit 330 is configured to drives the carriage motor in response to acontrol signal from the printing control unit 221. The carriage 500 isconfigured to, with this action, reciprocate along the carriage guideshaft 331. Further, although not illustrated, the carriage conveyanceunit 330 includes a carriage position sensor configured to detect aposition of the carriage 500. The printing control unit 221 isconfigured to control a moving amount of the carriage 500 with referenceto a signal from the carriage position sensor. The carriage 500 isconfigured to reciprocate in the main scanning direction X as describedabove with discharge of ink from the printing head 400, and the medium Pis conveyed in the sub scanning direction Y. In this manner, an image orthe like is printed on the medium P.

The printing head 400 is provided with four printing heads in total.Each printing head includes two printing chips with a plurality ofnozzles (nozzle groups) discharging inks of colors (C, M, Y, and K). Theprinting head 400 is mounted to the carriage 500, and is configured toreciprocate on the medium P in the main scanning direction X along withreciprocation of the carriage 500.

In the First Exemplary Embodiment, the main scanning direction Xcorresponds to a subordinate concept to the second direction describedin Summary. Further, the sub scanning direction Y and the mediumconveyance unit 320 correspond to a subordinate concept to the firstdirection in Summary and a subordinate concept to the conveyance unit inSummary, respectively.

A2. Detailed Configuration of Printing Head:

FIG. 2 is an explanatory view illustrating a detailed configuration ofthe printing head 400. In FIG. 2, the configuration of the printing head400 is illustrated when viewed in a direction from the medium P to thecarriage 500. The printing head 400 includes a first printing head Hd1,a second printing head Hd2, a third printing head Hd3, and a fourthprinting head Hd4. Each of the printing heads Hd1 to Hd4 includes twoprinting chips. The two printing chips of each of the printing heads Hd1to Hd4 are similarly arranged at similar positions on each of theprinting heads Hd1 to Hd4. Specifically, the two printing chips of eachof the printing heads Hd1 to Hd4 are arranged so as to partially overlapwith each other in the main scanning direction X.

The first printing head Hd1 includes a first printing chip Ch1 and asecond printing chip Ch2. The second printing head Hd2 includes a thirdprinting chip Ch3 and a fourth printing chip Ch4. The third printinghead Hd3 includes a fifth printing chip Ch5 and a sixth printing chipCh6. The fourth printing head Hd4 includes a seventh printing chip Ch7and an eighth printing chip Ch8. Each of the printing chips Ch1 to Ch8is a printing chip obtained by chipping an ink discharge mechanismincluding a piezoelectric element, an ink chamber, and a nozzle throughapplication of a semiconductor processing technique.

The first printing chip Ch1 includes two nozzle rows (nozzle groups)from which inks of two respective colors are discharged. Specifically,the first printing chip Ch1 includes a first nozzle row CL1 fordischarging ink of cyan (C) and a second nozzle row ML1 for dischargingink of magenta (M). Similarly, the second printing chip Ch2 includes athird nozzle row CL2 for discharging ink of cyan (C) and a fourth nozzlerow ML2 for discharging ink of magenta (M). As described above, the twoprinting chips Ch1 and Ch2 each include the two nozzle rows fordischarging inks of the same color combination.

Similarly, the third printing chip Ch3 includes a fifth nozzle row YL3for discharging ink of yellow (Y) and a sixth nozzle row KL3 fordischarging ink of black (K). The fourth printing chip Ch4 includes aseventh nozzle row YL4 for discharging ink of yellow (Y) and an eighthnozzle row KL4 for discharging ink of black (K).

The fifth printing chip Ch5 includes a ninth nozzle row KL5 fordischarging ink of black (K) and a tenth nozzle row YL5 for dischargingink of yellow (Y). The sixth printing chip Ch6 includes an eleventhnozzle row KL6 for discharging ink of black (K) and a twelfth nozzle rowYL6 for discharging ink of yellow (Y).

The seventh printing chip Ch7 includes a thirteenth nozzle row ML7 fordischarging ink of magenta (M) and a fourteenth nozzle row CL7 fordischarging ink of cyan (C). The eighth printing chip Ch8 includes afifteenth nozzle row ML8 for discharging ink of magenta (M) and asixteenth nozzle row CL8 for discharging ink of cyan (C).

The two nozzle rows in each of the printing chips Ch1 to Ch8 arearranged away from each other in the main scanning direction X.Specifically, the first nozzle row CL1 and the second nozzle row ML1 arearranged away from each other in the main scanning direction X.Similarly, the third nozzle CL2 and the fourth nozzle row ML2 arearranged away from each other in the main scanning direction X. Further,the fifth nozzle row YL3 and the sixth nozzle row KL3 are arranged awayfrom each other in the main scanning direction X. The seventh nozzle rowYL4 and the eighth nozzle row KL4 are arranged away from each other inthe main scanning direction X. The ninth nozzle row KL5 and the tenthnozzle row YL5 are arranged away from each other in the main scanningdirection X. The eleventh nozzle row KL6 and the twelfth nozzle row YL6are arranged away from each other in the main scanning direction X. Thethirteenth nozzle row ML7 and the fourteenth nozzle row CL7 are arrangedaway from each other in the main scanning direction X. The fifteenthnozzle row ML8 and the sixteenth nozzle row CL8 are arranged away fromeach other in the main scanning direction X.

An input signal is supplied from the printing control unit 221 to eachof the printing chips Ch1 to Ch8, and ink is discharged from each nozzlerow in response to the input voltage.

As describe above, the two printing chips of each of the printing headsHd1 to Hd4 are arranged so as to partially overlap with each other inthe main scanning direction X. In the First Exemplary Embodiment, theprinting control unit 221 is configured to, in an area in which the twoprinting chips overlap with each other when viewed from the mainscanning direction X (hereinafter, referred to as “printing chipoverlapping area), causes ink to be discharged based on the nozzle usageratio set in advance so that an area in which the nozzle group in eachnozzle row simultaneously discharging ink of the same color are arrangeddoes not overlap with

another area in which the nozzle group in each nozzle row simultaneouslydischarging inks of different colors in the main scanning direction X.

As illustrated in FIG. 2, on the first printing head Hd1, the printingchip overlapping area ChOAr1 is an area in which a downstream end of thefirst printing chip Ch1 in the sub scanning direction Y and an upstreamend of the second printing chip Ch2 in the sub scanning direction Yoverlap with each other in the main scanning direction X. Further, onthe second printing head Hd2, a downstream end of the third printingchip Ch3 in the sub scanning direction Y and an upstream end of thefourth printing chip Ch4 in the sub scanning direction Y overlap witheach other in the main scanning direction X, and also overlap with theprinting chip overlapping area ChOAr1 in the main scanning direction X.On the third printing head Hd3, a downstream end of the fifth printingchip Ch5 in the sub scanning direction Y and an upstream end of thesixth printing chip Ch6 in the sub scanning direction Y overlap witheach other in the main scanning direction X, and also overlap with theprinting chip overlapping area ChOAr1 in the main scanning direction X.On the fourth printing head Hd4, a downstream end of the seventhprinting chip Ch7 in the sub scanning direction Y and an upstream end ofthe eighth printing chip Ch8 in the sub scanning direction Y overlapwith each other in the main scanning direction X, and also overlap withthe printing chip overlapping area ChOAr1 in the main scanning directionX. In other words, the printing chips Ch1 to Ch8 of the printing headsHd1 to Hd4 partially overlap with each other in the main scanningdirection X.

A3. Printing Chip Overlapping Area and Nozzle Usage Ratio:

FIG. 3 is an explanatory view illustrating a configuration of nozzlerows in the printing chip overlapping area ChOAr1 and the nozzle usageratio. In an upper part of FIG. 3, detailed configurations of the nozzlerows CL1, CL2, ML1, and ML2 in the printing chip overlapping area ChOAr1are illustrated. In a lower left part in FIG. 3, a nozzle usage ratio ofeach of the first nozzle row CL1 and the third nozzle row CL2 in theprinting chip overlapping area ChOAr1 is illustrated. In a lower rightpart in FIG. 3, a nozzle usage ration of each of the second nozzle rowML1 and the fourth nozzle row ML2 in the printing chip overlapping areaChOAr1 is illustrated. As illustrated in the upper part of FIG. 3, eachof the nozzle rows CL1, ML1, CL2, and ML2 includes a plurality ofnozzles 92 arrayed at a predetermined interval in a nozzle rowdirection. In the First Exemplary Embodiment, “nozzle row direction”indicates the sub scanning direction Y. Note that, the nozzle rowdirection is not limited to the sub scanning direction Y, and may be themain scanning direction X or a direction intersecting the main scanningdirection X and the sub scanning direction Y.

The nozzles 92 of the nozzle rows CL1, ML1, CL2, and ML2 in the printingchip overlapping area ChOAr1 are classified into a nozzle groupbelonging to two overlapping areas OAr1 and OAr2 and a nozzle groupbelonging to two single printing chip areas SAr1 and SAr2. In the FirstExemplary Embodiment, “overlapping area” is an area in which dots areformed on the medium P with ink discharged from the nozzles 92 of thetwo nozzle rows for discharging ink of the same color in the differentprinting chips, and an area in which the nozzle usage ratios of the twonozzle rows are neither 0% nor 100%. “Nozzle usage ratio” is a ratio ofinks discharged from the nozzles 92, and a ratio of the number of dots,which are formed by the nozzles 92 in one main scanning, to all the dotsin the main scanning direction X. In the above-mentioned nozzle usageratio setting map 234, a nozzle usage ratio for each nozzle row in thearea is set in advance.

Further, “single printing chip area” is an area in which dots are formedon the medium P with ink discharged from the nozzles 92 of each nozzlerow in the single printing chip. In FIG. 3, each of the nozzles 92 fordischarging ink the overlapping areas OAr1 and OAr2 is indicated with ablack circle, and each of the nozzles 92 for discharging ink in thesingle printing chip areas SAr1 and SAr2 is indicated with a hatchedcircle.

As illustrated in the upper part of FIG. 3, the first single printingchip area SAr1 is positioned on most downstream in the printing chipoverlapping area ChOAr1 in the sub scanning direction Y. In the firstsingle printing chip area SAr1, the nozzles 92 of the nozzle rows CL2and ML2 in the second printing chip Ch2 are caused to discharge ink sothat dots are formed on the medium P. The first overlapping area OAr1 ispositioned upstream of the first single printing chip area SAr1 in thesub scanning direction Y. In the first overlapping area OAr1, thenozzles 92 of the first nozzle row CL1 in the first printing chip Ch1and the nozzles 92 of the third nozzle row CL2 in the second printingchip Ch2 are caused to discharge ink of cyan so that dots are formed onthe medium P.

The second overlapping area OAr2 is positioned upstream of the firstoverlapping area OAr1 in the sub scanning direction Y. In the secondoverlapping area OAr2, the nozzles 92 of the second nozzle row ML1 inthe first printing chip Ch1 and the nozzles 92 of the fourth nozzle rowML2 in the second printing chip Ch2 are caused to discharge ink ofmagenta so that dots are formed on the medium P. The second singleprinting chip area SAr2 is positioned upstream of the second overlappingarea OAr2 in the sub scanning direction Y. In the second single printingchip area SAr2, the nozzles 92 of the nozzle rows CL1 and ML1 in thefirst printing chip Ch1 are caused to discharge ink so that dots areformed on the medium P.

In a case where the total number of nozzles 92 in the printing chipoverlapping area ChOAr1 is 40, the number of nozzles 92 in each of theoverlapping areas OAr1 and OAr2 and the number of nozzles 92 in each ofthe single printing chip areas SAr1 and SAr2 in the printing chipoverlapping area ChOAr1 are set as follows. That is, for example, thenumber of nozzles 92 in each of the overlapping areas OAr1 and OAr2 is12, and the number of nozzles 92 in each of the single printing chipareas SAr1 and SAr2 is eight. Note that, the total number of nozzles 92in the printing chip overlapping area ChOAr1, the number of nozzles 92in each of the overlapping areas OAr1 and OAr2, and the number ofnozzles 92 in each of the single printing chip areas SAr1 and SAr2 arenot limited to the above-mentioned example, and may be any number.

The first overlapping area OAr1 and the second overlapping area OAr2 donot overlap with each other when viewed from the main scanning directionX. The reason for this is as follows. That is, in a case where landingposition deviation of ink droplets is caused in the first overlappingarea OAr1 and the second overlapping area OAr2 due to, for example,variation of an ink discharge amount and an ink discharge speed and thelike caused by a drive frequency difference among the nozzles 92,concentration of uneven density (streaks) in the main scanning directionX in a printing image can be suppressed. In this manner, degradation ofprinting image quality can be suppressed.

In each of the lower right and left parts of FIG. 3, a vertical axisindicates a nozzle usage ratio, and a horizontal axis indicates theprinting chip overlapping area ChOAr1. The horizontal axis correspondsto positions of the nozzles 92 in the sub scanning direction Y in theprinting chip overlapping area ChOAr1, which are illustrated in theupper part of FIG. 3. In the lower left part of FIG. 3, as indicatedwith the two-dot chain line, the nozzle usage ratio of the nozzles 92 ofthe first nozzle row CL1 is set to 100% from upstream in the subscanning direction Y to most upstream in the first overlapping areaOAr1. The nozzle usage ratio of the nozzles 92 of the first nozzle rowCL1 may be set so as to be gradually reduced from upstream to downstreamin the sub scanning direction Y in the first overlapping area OAr1. Thenozzle usage ratio of the nozzle 92 is set to 0% on most downstream inthe first overlapping area OAr1. The nozzle usage ratio of the nozzles92 of the first nozzle row CL1 is set to 0% on downstream of the firstoverlapping area OAr1 in the sub scanning direction Y.

In the lower left part of FIG. 3, as indicated with the solid line, thenozzle usage ratio of the nozzles 92 of the third nozzle row CL2 is setto 0% from upstream in the sub scanning direction Y to most upstream inthe first overlapping area OAr1. In the first overlapping area OAr1, thenozzle usage ratio of the nozzles 92 of the third nozzle row CL2 is setso as to be gradually increased from upstream to downstream in the subscanning direction Y. The nozzle usage ratio of the nozzle 92 is set to100% on most downstream in the first overlapping area OAr1. The nozzleusage ratio of the nozzles 92 of the third nozzle row CL2 is set to 100%on downstream of the first overlapping area OAr1 in the sub scanningdirection Y.

In the lower right part of FIG. 3, as indicated with the dashed line,the nozzle usage ratio of the nozzles 92 of the second nozzle row ML1 isset to 100% from upstream in the sub scanning direction Y to mostupstream in the second overlapping area OAr2. In the second overlappingarea OAr2, the nozzle usage ratio of the nozzles 92 of the second nozzlerow ML1 is set so as to be gradually reduced from upstream to downstreamin the sub scanning direction Y. The nozzle usage ratio of the nozzle 92is set to 0% on most downstream in the second overlapping area OAr2. Thenozzle usage ratio of the nozzles 92 of the second nozzle row ML1 is setto 0% on downstream of the second overlapping area OAr2 in the subscanning direction Y.

In the lower right part of FIG. 3, as indicated with the one-dot chainline, the nozzle usage ratio of the nozzles 92 of the fourth nozzle rowML2 is set to 100% from upstream in the sub scanning direction Y to mostupstream in the second overlapping area OAr2. In the second overlappingarea OAr2, the nozzle usage ratio of the nozzles 92 of the fourth nozzlerow ML2 is set so as to be gradually increased from upstream todownstream in the sub scanning direction Y. The nozzle usage ratio ofthe nozzle 92 is set to 100% on most downstream in the secondoverlapping area OAr2. The nozzle usage ratio of the nozzles 92 of thefourth nozzle row ML2 is set to 100% on downstream of the secondoverlapping area OAr2 in the sub scanning direction Y.

As illustrated in the lower left part of FIG. 3, in the firstoverlapping area OAr1, the nozzle usage ratio of the first nozzle rowCL1 and the nozzle usage ratio of the third nozzle row CL2 is set tovalues, which are neither 0% nor 100%. Further, the nozzle usage ratiosare set so that the sum of the nozzle usage ratios of the nozzle rowsCL1 and CL2 is 100%. As illustrated in the lower right part of FIG. 3,in the second overlapping area OAr2, the nozzle usage ratio of thesecond nozzle row ML1 and the nozzle usage ratio of the fourth nozzlerow ML2 are set to values, which are neither 0% nor 100%. The nozzleusage ratios are set so that the sum of the nozzle usage ratios of thenozzle rows ML1 and ML2 is 100%.

A4. Printing Processing:

FIG. 4 is a flowchart illustrating a process procedure of the printingprocessing. In the First Exemplary Embodiment, the printing data isgenerated so that the first overlapping area OAr1 and the secondoverlapping area OAr2 do not overlap with each other when viewed fromthe main scanning direction X and the nozzle usage ratio in each of theoverlapping areas OAr1 and OAr2 is set to the nozzle usage ratioillustrated in FIG. 3. Then, printing is performed based on the printingdata. Now, detailed description is given.

As illustrated in FIG. 4, the printing processing is started when, forexample, a user designates the image data and instructs to performprinting by the printing control device 10. The printing control unit221 performs resolution conversion processing on the designated imagedata (Step S100). As the image data being a processing target, imagedata generated by an application (not illustrated) in the printingcontrol device 10 or image data received from an input interface (notillustrated) are exemplified. In the First Exemplary Embodiment, theimage data is formed of gradation values of colors, red (R), green (G),and blue (B). In Step S100, the printing control unit 221 converts aresolution of the image data to a resolution for performing printing onthe medium P.

The printing control unit 221 performs color conversion processing (StepS105). Specifically, with reference to a color conversion table (notillustrated) stored in the memory 230, the printing control unit 221converts the RGB image data to CMYK data of 256-level gradation withgradation values of colors (C, M, Y, and K) of ink used in the printingapparatus 100.

The printing control unit 221 performs halftone processing on the CMYKdata to which the color conversion has been applied (Step S110).Specifically, with reference to the first dither mask 231 and the seconddither mask 232 stored in the memory 230, the printing control unit 221converts the gradation values of 256 levels (steps) of the CMYK data tofour-level gradation values (two-bit data) that can be expressed withthe printing apparatus 100. The four levels include two patterns ofsingle use, combination use, and disuse of two kinds of dots havingdifferent sizes (a large dot and a small dot). In Step S110, withreference to the mask selecting map 233, the printing control unit 221acquires each threshold value from a corresponding dither mask.Specifically, the printing control unit 221 generates the CMYK datathrough use of the threshold value set in the first dither mask 231 forthe overlapping areas OAr1 and OAr2, and generates the CMYK data throughuse of the threshold value set in the second dither mask 232 for thesingle printing chip areas SAr1 and SAr2.

The printing control unit 221 performs rasterizing processing, based onthe image data to which the halftone processing has been applied, andoutputs the resultant printing data (Step S115). Specifically, theprinting control unit 221 generates the printing data by associating theimage data to which the halftone processing has been applied with thenozzles 92, based on the above-mentioned nozzle usage ratios, and addinga printing control command.

When the generation of the printing data is completed, the printingcontrol unit 221 controls the carriage conveyance unit 330 and themedium conveyance unit 320 to perform printing (Step S120).Specifically, a plurality of times of scanning of the carriageconveyance unit 330 and discharge of ink onto the medium P, andconveyance of the medium P to downstream in the sub scanning direction Yare alternately repeated. In this manner, dots are formed on the mediumP.

In the printing apparatus 100 having the above-mentioned configurationaccording to the First Exemplary Embodiment, in the printing chipoverlapping area ChOAr1, ink is discharged so that the first overlappingarea CAr1 and the second overlapping area OAr2 do not overlap with eachother when viewed from the main scanning direction X. Thus, in a casewhere landing position deviation of ink droplets is caused both in thefirst overlapping area CAr1 and the second overlapping area OAr2, theareas in which landing position deviation is caused are dispersed in themain scanning direction X so that uneven density is prevented fromappearing in an overlapping manner in the main scanning direction X inthe printing image. In this manner, degradation of the printing imagequality in the printing chip overlapping area ChOAr1 can be suppressed.

B. Second Exemplary Embodiment

The printing apparatus 100 and the printing head 400 in a SecondExemplary Embodiment are similar to the printing apparatus 100 and theprinting head 400 in the First Exemplary Embodiment, which areillustrated in FIG. 1 and FIG. 2. Thus, detailed description thereof isomitted. Further, the process procedure of the printing processing inthe Second Exemplary Embodiment is similar to the process procedure ofthe printing processing in the First Exemplary Embodiment, which isillustrated in FIG. 4. Thus, detailed description thereof is omitted.

FIG. 5 is an explanatory view illustrating a printing chip overlappingarea ChOAr2 in the Second Exemplary Embodiment. The printing chipoverlapping area ChOAr1 in the First Exemplary Embodiment is the area inwhich the first printing chip Ch1 and the second printing chip Ch2 onthe first printing head Hd1 overlap with each other in the main scanningdirection X. As compared to this, the printing chip overlapping areaChOAr2 in the Second Exemplary Embodiment is an area in which theprinting chips Ch1 to Ch8 on the printing head 400 overlap with eachother in the main scanning direction X.

The nozzles 92 of the nozzle rows CL1, ML1, CL2, ML2, YL3, KL3, YL4,KL4, KL5, YL5, KL6, YL6, ML7, CL7, ML8, and CL8 in the printing chipoverlapping area ChOAr2 are classified into a nozzle group belonging totwo cyan overlapping areas COAr1 and COAr2, a nozzle group belonging totwo magenta overlapping areas MOAr1 and MOAr2, a nozzle group belongingto two yellow overlapping areas YOAr1 and YOAr2, and a nozzle groupbelonging to two black overlapping areas KOAr1 and KOAr2.

As illustrated in FIG. 5, in the first cyan overlapping area COAr1, thenozzles 92 of the first nozzle row CL1 in the first printing chip Ch1and the nozzles 92 of the third nozzle row CL2 in the second printingchip Ch2 are caused to discharge ink of cyan to form dots on the mediumP. In the second cyan overlapping area COAr2, the nozzles 92 of thefourteenth nozzle CL7 in the seventh printing chip Ch7 and the nozzles92 of the sixteenth nozzle row CL8 in the eighth printing chip Ch8 arecaused to discharge ink of cyan to form dots on the medium P.

In the first magenta overlapping area MOAr1, the nozzles 92 of thesecond nozzle row ML1 in the first printing chip Ch1 and the nozzles 92of the fourth nozzle row ML2 in the second printing chip Ch2 are causedto discharge ink of magenta to form dots on the medium P. In the secondmagenta overlapping area MOAr2, the nozzles 92 of the thirteenth nozzlerow ML7 in the seventh printing chip Ch7 and the nozzles 92 of thefifteenth nozzle row ML8 in the eighth printing chip Ch8 are caused todischarge ink of magenta to form dots on the medium P.

In the first yellow overlapping area YOAr1, the nozzles 92 of the tenthnozzle row YL5 in the fifth printing chip Ch5 and the nozzles 92 of thetwelfth nozzle row YL6 in the sixth printing chip Ch6 are caused todischarge ink of yellow to form dots on the medium P. In the secondyellow overlapping area YOAr2, the nozzles 92 of the fifth nozzle rowYL3 in the third printing chip Ch3 and the nozzles 92 of the seventhnozzle row YL4 in the fourth printing chip Ch4 are caused to dischargeink of yellow to form dots on the medium P.

In the first black overlapping area KOAr1, the nozzles 92 of the sixthnozzle row KL3 in the third printing chip Ch3 and the nozzles 92 of theeighth nozzle row KL4 in the fourth printing chip Ch4 are caused todischarge ink of black to form dots on the medium P. In the second blackoverlapping area KOAr2, the nozzles 92 of the ninth nozzle row KL5 inthe fifth printing chip Ch5 and the nozzles 92 of the eleventh nozzlerow KL6 in the sixth printing chip Ch6 are caused to discharge ink ofblack to form dots on the medium P.

As illustrated in FIG. 5, the black overlapping areas KOAr1 and KOAr2and the yellow overlapping areas YOAr1 and YOAr2 completely overlap witheach other when viewed from the main scanning direction X. Specifically,the first black overlapping area KOAr1 and the first yellow overlappingarea YOAr1 completely overlap with each other when viewed from the mainscanning direction X. The second black overlapping area KOAr2 and thesecond yellow overlapping area YOAr2 completely overlap with each otherwhen viewed from the main scanning direction X.

Meanwhile, the cyan overlapping areas and the magenta overlapping areasin the two printing chips do not overlap with each other when viewedfrom the main scanning direction X. Specifically, in the first printingchip Ch1 and the second printing chip Ch2, the first cyan overlappingarea COAr1 and the first magenta overlapping area MOAr1 do not overlapwith each other when viewed from the main scanning direction X. In theseventh printing chip Ch7 and the eighth printing chip Ch8, the secondcyan overlapping area COAr2 and the second magenta overlapping areaMOAr2 do not overlap with each other when viewed from the main scanningdirection X.

In the printing chip overlapping area ChOAr2, the cyan overlapping areasdo not overlap with each other when viewed from the main scanningdirection X. Further, the magenta overlapping areas do not overlap witheach other when viewed from the main scanning direction X. Specifically,in the printing chip overlapping area ChOAr2, the first cyan overlappingarea COAr1 and the second cyan overlapping area COAr2 do not overlapwith each other when viewed from the main scanning direction X, and arearranged away from each other in the sub scanning direction Y as much aspossible. In the printing chip overlapping area ChOAr2, the firstmagenta overlapping area MOAr1 and the second magenta overlapping areaMOAr2 do not overlap with each other when viewed from the main scanningdirection X, and are arranged away from each other in the sub scanningdirection Y as much as possible.

The reasons for overlapping the black overlapping areas KOAr1 and KOAr2and the yellow overlapping areas YOAr1 and YOAr2 with each other whenviewed from the main scanning direction X as described above are asfollows. A large amount of ink of black and a large amount of ink ofyellow are less liable to be discharged at the same time. Thus, in acase where landing position deviation of ink droplets is caused due tovariation of an ink discharge amount and an ink discharge speed and thelike caused by a drive frequency difference among the nozzles 92,landing position deviation is less liable to be caused at the same timein the black overlapping areas KOAr1 and KOAr2 and the yellowoverlapping areas YOAr1 and YOAr2. Therefore, in the printing image, theprinting image quality is less liable to be degraded.

In the structure of the printing apparatus 100, the total number ofnozzles 92 in the printing chip overlapping area ChOAr2 is set inadvance. With this, the black overlapping areas KOAr1 and KOAr2 and theyellow overlapping areas YOAr1 and YOAr2 completely overlap with eachother. Accordingly, the number of nozzles 92 can be secured so that theoverlapping areas COAr1, COAr2, MOAr1, and MOAr2 of the colors otherthan black and yellow do not overlap with each other when viewed fromthe main scanning direction X, and are positioned away from each otherin the sub scanning direction Y as much as possible.

Note that, in a case where the cyan overlapping areas COAr1 and COAr2and the magenta overlapping areas MOAr1 and MOAr2 are overlapping areasin different printing chips, the cyan overlapping areas COAr1 and COAr2and the magenta overlapping areas MOAr1 and MOAr2 may overlap with eachother when viewed from the main scanning direction X. Specifically, asillustrated in FIG. 5, the second cyan overlapping area COAr2 in theseventh printing chip Ch7 and the eighth printing chip Ch8 and the firstmagenta overlapping area MOAr1 in the first printing chip Ch1 and thesecond printing chip Ch2 partially overlap with each other when viewedfrom the main scanning direction X.

Each of FIG. 6, FIG. 7, FIG. 8, and FIG. 9 is an explanatory viewillustrating a nozzle usage ratio of the nozzles 92 in the printing chipoverlapping area ChOAr2 in the Second Exemplary Embodiment. FIG. 6illustrates a nozzle usage ratio of each of the nozzle rows CL1, CL2,CL7, and CL8 for discharging ink of cyan. FIG. 7 illustrates a nozzleusage ratio of each of the nozzle rows ML1, ML2, ML7, and ML8 fordischarging ink of magenta. FIG. 8 illustrates a nozzle usage ratio ofeach of the nozzle rows YL3, YL4, YL5, and YL6 for discharging ink ofyellow. FIG. 9 illustrates a nozzle usage ratio of each of the nozzlerows KL3, KL4, KL5, and KL6 for discharging ink of black.

In an upper part of FIG. 6, as indicated with the two-dot chain line,the nozzle usage ratio of the nozzles 92 of the first nozzle row CL1 isset so as to be gradually reduced from upstream to downstream in the subscanning direction Y in the first cyan overlapping area COAr1. Thenozzle usage ratio of the nozzle 92 is set to 0% on most downstream inthe first cyan overlapping area COAr1. The nozzle usage ratio of thenozzles 92 of the first nozzle row CL1 is set to 0% on downstream of thefirst cyan overlapping area COAr1 in the sub scanning direction Y.

In the upper part of FIG. 6, as indicated with the solid line, in thefirst cyan overlapping area COAr1, the nozzle usage ratio of the nozzles92 of the third nozzle row CL2 is set so as to be gradually increasedfrom upstream to downstream in the sub scanning direction Y. The nozzleusage ratio of the nozzle 92 may be set to 100% on most downstream inthe first cyan overlapping area COAr1. The nozzle usage ratio of thenozzles 92 of the third nozzle row CL2 is set to 100% on downstream ofthe first cyan overlapping area COAr1 in the sub scanning direction Y.

In a lower part of FIG. 6, as indicated with the dashed line, the nozzleusage ratio of the nozzles 92 of the fourteenth nozzle row CL7 is set to100% from upstream in the sub scanning direction Y to most upstream inthe second cyan overlapping area COAr2. In the second cyan overlappingarea COAr2, the nozzle usage ratio of the nozzles 92 of the fourteenthnozzle row CL7 is set so as to be gradually reduced from upstream todownstream in the sub scanning direction Y. The nozzle usage ratio ofthe nozzle 92 is set to 0% on most downstream in the second cyanoverlapping area COAr2. The nozzle usage ratio of the nozzles 92 of thefourteenth nozzle row CL7 is set to 0% on downstream of the second cyanoverlapping area COAr2 in the sub scanning direction Y.

In the lower part of FIG. 6, as indicated with the two-dot chain line,the nozzle usage ratio of the nozzles 92 of the sixteenth nozzle row CL8is set to 0% from upstream in the sub scanning direction Y to mostupstream in the second cyan overlapping area COAr2. In the second cyanoverlapping area COAr2, the nozzle usage ratio of the nozzles 92 of thesixteenth nozzle row CL8 is set so as to be gradually increased fromupstream to downstream in the sub scanning direction Y. The nozzle usageratio of the nozzle 92 is set to 100% on most downstream in the secondcyan overlapping area COAr2. The nozzle usage ratio of the nozzles 92 ofthe sixteenth nozzle row CL8 is set to 100% on downstream of the secondcyan overlapping area COAr2 in the sub scanning direction Y.

In an upper part of FIG. 7, as indicated with the two-dot chain line,the nozzle usage ratio of the nozzles 92 of the second nozzle row ML1 isset to 100% from upstream in the sub scanning direction Y to mostupstream in the first magenta overlapping area MOAr1. In the firstmagenta overlapping area MOAr1, the nozzle usage ratio of the nozzles 92of the second nozzle row ML1 is set so as to be gradually reduced fromupstream to downstream in the sub scanning direction Y. The nozzle usageratio of the nozzle 92 is set to 0% on most downstream in the firstmagenta overlapping area MOAr1. The nozzle usage ratio of the nozzles 92of the second nozzle row ML1 is set to 0% on downstream of the firstmagenta overlapping area MOAr1 in the sub scanning direction

In the upper part of FIG. 7, as indicated with the solid line, thenozzle usage ratio of the nozzles 92 of the fourth nozzle row ML2 is setto 0% from upstream in the sub scanning direction Y to most upstream inthe first magenta overlapping area MOAr1. In the first magentaoverlapping area MOAr1, the nozzle usage ratio of the nozzles 92 of thefourth nozzle row ML2 is set so as to be gradually increased fromupstream to downstream in the sub scanning direction Y. The nozzle usageratio of the nozzle 92 is set to 100% on most downstream in the firstmagenta overlapping area MOAr1. The nozzle usage ratio of the nozzles 92of the fourth nozzle row ML2 is set to 100% on downstream of the firstmagenta overlapping area MOAr1 in the sub scanning direction Y.

In a lower part of FIG. 7, as indicated with the dashed line, the nozzleusage ratio of the nozzles 92 of the thirteenth nozzle row ML7 is set to100% from upstream in the sub scanning direction Y to most upstream inthe second magenta overlapping area MOAr2. In the second magentaoverlapping area MOAr2, the nozzle usage ratio of the nozzles 92 of thethirteenth nozzle row ML7 is set so as to be gradually reduced fromupstream to downstream in the sub scanning direction Y. The nozzle usageratio of the nozzle 92 is set to 0% on most downstream in the secondmagenta overlapping area MOAr2.

In the lower part of FIG. 7, as indicated with the two-dot chain line,the nozzle usage ratio of the nozzles 92 of the fifteenth nozzle row ML8is set to 0% from upstream in the sub scanning direction Y to mostupstream in the second magenta overlapping area MOAr2. In the secondmagenta overlapping area MOAr2, the nozzle usage ratio of the nozzles 92of the fifteenth nozzle row ML8 is set so as to be gradually increasedfrom upstream to downstream in the sub scanning direction Y. The nozzleusage ratio of the nozzle 92 is set to 100% on most downstream in thesecond magenta overlapping area MOAr2.

In an upper part of FIG. 8, as indicated with the two-dot chain line,the nozzle usage ratio of the nozzles 92 of the fifth nozzle row YL3 isset to 100% from upstream in the sub scanning direction Y to mostupstream in the second yellow overlapping area YOAr2. In the secondyellow overlapping area YOAr2, the nozzle usage ratio of the nozzles 92of the fifth nozzle row YL3 is set so as to be gradually reduced fromupstream to downstream in the sub scanning direction Y. The nozzle usageratio of the nozzle 92 is set to 0% on most downstream in the secondyellow overlapping area YOAr2. The nozzle usage ratio of the nozzles 92of the fifth nozzle row YL3 is set to 0% on downstream of the secondyellow overlapping area YOAr2 in the sub scanning direction

In an upper part of FIG. 8, as indicated with the solid line, the nozzleusage ratio of the nozzles 92 of the seventh nozzle row YL4 is set to 0%from upstream in the sub scanning direction Y to most upstream in thesecond yellow overlapping area YOAr2. In the second yellow overlappingarea YOAr2, the nozzle usage ratio of the nozzles 92 of the seventhnozzle row YL4 is set so as to be gradually increased from upstream todownstream in the sub scanning direction Y. The nozzle usage ratio ofthe nozzle 92 is set to 100% on most downstream in the second yellowoverlapping area YOAr2. The nozzle usage ratio of the nozzles 92 of theseventh nozzle row YL4 is set to 100% on downstream of the second yellowoverlapping area YOAr2 in the sub scanning direction

In a lower part of FIG. 8, as indicated with the dashed line, the nozzleusage ratio of the nozzles 92 of the tenth nozzle row YL5 is set to 100%from upstream in the sub scanning direction Y to most upstream in thefirst yellow overlapping area YOAr1. In the first yellow overlappingarea YOAr1, the nozzle usage ratio of the nozzles 92 of the tenth nozzlerow YL5 is set so as to be gradually reduced from upstream to downstreamin the sub scanning direction Y. The nozzle usage ratio of the nozzle 92is set to 0% on most downstream in the first yellow overlapping areaYOAr1. The nozzle usage ratio of the nozzles 92 of the tenth nozzle rowYL5 is set to 0% on downstream of the first yellow overlapping areaYOAr1 in the sub scanning direction Y.

In a lower part of FIG. 8, as indicated with the two-dot chain line, thenozzle usage ratio of the nozzles 92 of the twelfth nozzle row YL6 isset to 0% from upstream in the sub scanning direction Y to most upstreamin the first yellow overlapping area YOAr1. In the first yellowoverlapping area YOAr1, the first yellow overlapping area YOAr1, thenozzle usage ratio of the nozzles 92 of the twelfth nozzle row YL6 isset so as to be gradually increased from upstream to downstream in thesub scanning direction Y. The nozzle usage ratio of the nozzle 92 is setto 100% on most downstream in the first yellow overlapping area YOAr1.The nozzle usage ratio of the nozzles 92 of the twelfth nozzle row YL6is set to 100% on downstream of the first yellow overlapping area YOAr1in the sub scanning direction Y.

In an upper part of FIG. 9, as indicated with the two-dot chain line,the nozzle usage ratio of the nozzles 92 of the sixth nozzle row KL3 isset to 100% from upstream in the sub scanning direction Y to mostupstream in the first black overlapping area KOAr1. In the first blackoverlapping area KOAr1, the nozzle usage ratio of the nozzles 92 of thesixth nozzle row KL3 is set so as to be gradually reduced from upstreamto downstream in the sub scanning direction Y. The nozzle usage ratio ofthe nozzle 92 is set to 0% on most downstream in the first blackoverlapping area KOAr1. The nozzle usage ratio of the nozzles 92 of thesixth nozzle row KL3 is set to 0% on downstream of the first blackoverlapping area KOAr1 in the sub scanning direction Y.

In the upper part of FIG. 9, as indicated with the solid line, thenozzle usage ratio of the nozzles 92 of the eighth nozzle row KL4 is setto 0% from upstream in the sub scanning direction Y to most upstream inthe first black overlapping area KOAr1. In the first black overlappingarea KOAr1, the nozzle usage ratio of the nozzles 92 of the eighthnozzle row KL4 is set so as to be gradually increased from upstream todownstream in the sub scanning direction Y. The nozzle usage ratio ofthe nozzle 92 is set to 100% on most downstream in the first blackoverlapping area KOAr1. The nozzle usage ratio of the nozzles 92 of theeighth nozzle row KL4 is set to 100% on downstream of the first blackoverlapping area KOAr1 in the sub scanning direction Y.

In a lower part of FIG. 9, as indicated with the dashed line, the nozzleusage ratio of the nozzles 92 of the ninth nozzle row KL5 is set to 100%from upstream in the sub scanning direction Y to most upstream in thesecond black overlapping area KOAr2. In the second black overlappingarea KOAr2, the nozzle usage ratio of the nozzles 92 of the ninth nozzlerow KL5 is set so as to be gradually reduced from upstream to downstreamin the sub scanning direction Y. The nozzle usage ratio of the nozzle 92is set to 0% on most downstream in the second black overlapping areaKOAr2. The nozzle usage ratio of the nozzles 92 of the ninth nozzle rowKL5 is set to 0% on downstream of the second black overlapping areaKOAr2 in the sub scanning direction Y.

In the lower part of FIG. 9, as indicated with the two-dot chain line,the nozzle usage ratio of the nozzles 92 of the eleventh nozzle row KL6is set to 0% from upstream in the sub scanning direction Y to mostupstream in the second black overlapping area KOAr2. In the second blackoverlapping area KOAr2, the nozzle usage ratio of the nozzles 92 of theeleventh nozzle row KL6 is set so as to be gradually increased fromupstream to downstream in the sub scanning direction Y. The nozzle usageratio of the nozzle 92 is set to 100% on most downstream in the secondblack overlapping area KOAr2. The nozzle usage ratio of the nozzles 92of the eleventh nozzle row KL6 is set to 100% on downstream of thesecond black overlapping area KOAr2 in the sub scanning direction Y.

As understood by comparison with FIG. 6, FIG. 7, FIG. 8, and FIG. 9, inany area of the overlapping areas COAr1, COAr2, MOAr1, MOAr2, YOAr1,YOAr2, KOAr1, and KOAr2, the nozzle usage ratios of the nozzle rows ineach of the overlapping areas are set to a value, which is neither 0%nor 100%. Further, the nozzle usage ratios are set so that the sum ofthe nozzle usage ratios of the nozzles rows in the overlapping areas is100%.

Note that, in the Second Exemplary Embodiment, the black overlappingareas KOAr1 and KOAr2 correspond to a subordinate concept to the firstoverlapping area described in Summary. The yellow overlapping areasYOAr1 and YOAr2 correspond to a subordinate concept to the secondoverlapping area described in Summary. The sixth nozzle row KL3 and theninth nozzle row KL5 correspond to a subordinate concept to the firstnozzle row described in Summary. The eighth nozzle row KL4 and theeleventh nozzle row KL6 correspond to a subordinate concept to the thirdnozzle row described in Summary. The fifth nozzle row YL3 and the tenthnozzle row YL5 correspond to a subordinate concept to the second nozzlerow described in Summary. The seventh nozzle row YL4 and the twelfthnozzle row YL6 correspond to a subordinate concept to the fourth nozzlerow described in Summary. The first nozzle row CL1 and the second nozzlerow ML1 correspond to a subordinate concept to the fifth nozzle rowdescribed in Summary. The third nozzle row CL2 and the fourth nozzle rowML2 correspond to a subordinate concept to the sixth nozzle rowdescribed in Summary.

In the printing apparatus 100 having the above-mentioned configurationaccording to the Second Exemplary Embodiment, the same effects as thosein the First Exemplary Embodiment can be exerted. Additionally, in theprinting chip overlapping area ChOAr2, the printing control unit 221causes ink to be discharged so that the first black overlapping areaKOAr1 and the first yellow overlapping area YOAr1 completely overlapwith each other when viewed from the main scanning direction X, and alsocauses ink to be discharged so that the second black overlapping areaKOAr2 and the second yellow overlapping area YOAr2 completely overlapwith other when viewed from the main scanning direction X. Thus, ascompared to the configuration in which ink is discharged so that theblack overlapping areas KOAr1 and KOAr2 and the yellow overlapping areasYOAr1 and YOAr2 do not overlap with each other when viewed from the mainscanning direction X, the overlapping areas COAr1, COAr2, MOAr1, andMOAr2 of the colors other than black and yellow, the black overlappingareas KOAr1 and KOAr2, and the yellow overlapping areas YOAr1 and YOAr2can be arranged at the positions away from each other in the subscanning direction Y. Further, there can be secured the area (nozzlegroup) in which the cyan overlapping areas COAr1 and COAr2 are arrangedso as not to overlap with each other when viewed from the main scanningdirection X and the area (nozzle group) in which the magenta overlappingareas MOAr1 and MOAr2 are arranged so as not to overlap with each otherwhen viewed from the main scanning direction X. Additionally, theprinting apparatus 100 can be reduced in size.

C. Other Exemplary Embodiments C1. Exemplary Embodiment 1

In the above-mentioned First Exemplary Embodiment, the first overlappingarea OAr1 and the second overlapping area OAr2 do not overlap with eachother in the main scanning direction X. However, the invention is notlimited thereto. For example, the first overlapping area OAr1 and thesecond overlapping area OAr2 may partially overlap with each other inthe main scanning direction X. That is, the first overlapping area OAr1and the second overlapping area OAr2 may be arranged so as not to atleast partially overlap with each other in the main scanning directionX. Such configuration also exerts effects similar to those in theabove-mentioned First Exemplary Embodiment.

C2. Exemplary Embodiment 2

In the above-mentioned Second Exemplary Embodiment, the first blackoverlapping area KOAr1 and the first yellow overlapping area YOAr1completely overlap with each other when viewed from the main scanningdirection X, and also the second black overlapping area KOAr2 and thesecond yellow overlapping area YOAr2 completely overlap with each otherwhen viewed from the main scanning direction X. However, the inventionis not limited this configuration. For example, the first blackoverlapping area KOAr1 and the first yellow overlapping area YOAr1 maypartially overlap with each other when viewed from the main scanningdirection X. Further, for example, the second black overlapping areaKOAr2 and the second yellow overlapping area YOAr2 may partially overlapwith each other when viewed from the main scanning direction X. Suchconfiguration also exerts effects similar to those in theabove-mentioned Second Exemplary Embodiment.

C3. Exemplary Embodiment 3

In each of the above-mentioned exemplary embodiments, the printingapparatus 100 is a serial ink jet-type printer. However, in place of aserial ink jet-type printer, a line printer for performing line printingmay be used. Such configuration also exerts effects similar to those inthe above-mentioned exemplary embodiments.

C4. Exemplary Embodiment 4

In each of the above-mentioned exemplary embodiments, the printingcontrol unit 221 performs single pass printing in which a raster iscompleted by one main scanning of the printing head 400. In place ofthis, there may be performed a multi-pass printing in which rasters arecompleted by a plurality of times of main scanning of the printing head400. Such configuration also exerts effects similar to those in theabove-mentioned exemplary embodiments.

C5. Exemplary Embodiment 5

In the above-mentioned Second Exemplary Embodiment, in the configurationin which the printing head 400 further includes a nozzle row fordischarging ink of light black and a nozzle row for discharging ink ofmuch lighter black in addition to the nozzle rows KL3 to KL6 fordischarging ink of black, ink of black and ink of much lighter black maybe discharged so that the black overlapping area and a much lighterblack overlapping area overlap or completely overlap with each otherwhen viewed from the main scanning direction X. This is because asfollows. That is, a large amount of ink of black and a large amount ofink of much lighter black are less liable to be discharged at the sametime. Thus, in a case where landing position deviation of ink dropletsis caused, landing position deviation is less liable to be caused at thesame time in the black overlapping area and the lighter blackoverlapping area. Therefore, in the printing image, the printing imagequality is less liable to be degraded. Such configuration also exertseffects similar to those in the above-mentioned Second ExemplaryEmbodiment.

C6. Exemplary Embodiment 6

In each of the above-mentioned exemplary embodiments, the printingcontrol unit 221 generates the printing data. Instead, the printerdriver incorporated in the printing control device 10 may generate theprinting data. In this configuration, the printing control unit 221 canperform printing by controlling the conveyance motion of the medium P,the reciprocation operation of the carriage 500, and the dischargeoperation of the ink from the printing head 400, based on the printingdata received from the printing control device 10. Such configurationalso exerts effects similar to those in the above-mentioned exemplaryembodiments.

C7. Exemplary Embodiment 7

In each of the above-mentioned exemplary embodiments, the first printingchip Ch1 and the second printing chip Ch2 partially overlap with eachother when viewed from the main scanning direction X. However, theinvention is not limited to this configuration. For example, the firstprinting chip Ch1 and the second printing chip Ch2 may entirely overlapwith each other. In other words, in general, the first printing chip Ch1and the second printing chip Ch2 may be arranged so as to at leastpartially overlap with each other when viewed from the main scanningdirection X. Such configuration also exerts effects similar to those inthe above-mentioned exemplary embodiments.

C8. Exemplary Embodiment 8

In each of the above-mentioned exemplary embodiments, other devices mayhave at least part of the functions of the Printing apparatus 100. Forexample, the printing control device 10 may include the printing controlunit 221. Further, the printing apparatus 100 may have all the functionsof the printing control device 10. Such configuration can also exerteffects similar to those in the above-mentioned exemplary embodiments.

C9. Exemplary Embodiment 9

In each of the above-mentioned exemplary embodiments, part of theconfiguration achieved by the hardware may be replaced with software.Alternatively, part of the configuration achieved by the software may bereplaced with hardware. Further, in a case where part of the functionsor the entire functions of the invention is achieved by the software,the software (computer program) may be provided in a form stored in acomputer-readable recording medium. In the invention, “computer-readablerecording medium” is not limited to a portable recording medium such asa flexible disk and a CD-ROM, but includes various internal storagedevices such as a RAM and a ROM and various external storage devicesfixed to a computer such as a hard disk. In other words,“computer-readable recording medium” has a broad range of definitionincluding any recording device capable of non-transitorily and fixedlystoring data.

The invention is not limited to the exemplary embodiments describedabove. Rather, the invention can be achieved in various configurations,to an extent that such configurations fall within the scope of theinvention. For example, technical features of the exemplary embodiments,which correspond to the technical features of the embodiments describedin the summary of the invention, may be appropriately replaced orcombined to address some or all of the above-identified problems or toachieve some or all of the above-described advantages. When one of thetechnical features is not described as essential in the description, theone of the technical features may be appropriately deleted.

-   -   This application claims priority under 35 U.S.C. § 119 to        Japanese Patent Application No. 2018-021538, filed Feb. 9, 2018.        The entire disclosure of Japanese Patent Application No.        2018-021538 is hereby incorporated herein by reference.

What is claimed is:
 1. A printing apparatus for performing printing on amedium, the printing apparatus comprising: a printing head including afirst printing chip, a second printing chip, a third printing chip, afourth printing chip, a fifth printing chip, and a sixth printing chip,which are arranged to at least partially overlap with each other whenviewed from a second direction, the first printing chip including afirst nozzle row and a second nozzle row, which are away from each otherin the second direction intersecting a first direction, the first nozzlerow and the second nozzle row including a plurality of nozzles arrayedin the first direction for discharging ink onto the medium, the secondprinting chip including a third nozzle row and a fourth nozzle row,which are away from each other in the second direction, the third nozzlerow and the fourth nozzle row including a plurality of nozzles arrayedin the first direction for discharging the ink onto the medium, thethird printing chip including a fifth nozzle row and a sixth nozzle row,which are away from each other in the second direction, the fifth nozzlerow and the sixth nozzle row including a plurality of nozzles arrayed inthe first direction for discharging ink onto the medium, the fourthprinting chip including a seventh nozzle row and an eighth nozzle row,which are away from each other in the second direction, the seventhnozzle row and the eighth nozzle row including a plurality of nozzlesarrayed in the first direction for discharging ink onto the medium, thefifth printing chip including a ninth nozzle row and a tenth nozzle row,which are away from each other in the second direction, the ninth nozzlerow and the tenth nozzle row including a plurality of nozzles arrayed inthe first direction for discharging ink onto the medium, the sixthprinting chip including an eleventh nozzle row and a twelfth nozzle row,which are away from each other in the second direction, the eleventhnozzle row and the twelfth nozzle row including a plurality of nozzlesarrayed in the first direction for discharging ink onto the medium; aconveyance unit configured to convey the medium relatively to theprinting head; and a printing control unit configured to cause theprinting head to discharge the ink onto the medium, based on a nozzleusage ratio being a ratio of the ink discharged from each of theplurality of nozzles, wherein the first nozzle row, the third nozzlerow, the tenth nozzle row, and the twelfth nozzle row are configured todischarge black ink, the second nozzle row, the fourth nozzle row, theninth nozzle row, and the eleventh nozzle row are configured todischarge yellow ink, the fifth nozzle row and the seventh nozzle roware configured to discharge a first ink which is neither black ink noryellow ink, and the printing control unit is configured to cause the inkto be discharged so that a first distance is shorter than a seconddistance and a third distance, the first distance is a distance betweena center of a black ink overlapping area and a center of a yellow inkoverlapping area in the first direction, the second distance is adistance between a center of the black ink overlapping area and a centerof a first ink overlapping area in the first direction, the thirddistance is a distance between a center of the yellow ink overlappingarea and a center of the first ink overlapping area in the firstdirection, the black ink overlapping area being an area in which thenozzle usage ratio of the first nozzle row and the nozzle usage ratio ofthe third nozzle row are not 0% or 100%, the yellow ink overlapping areabeing an area in which the nozzle usage ratio of the ninth nozzle rowand the nozzle usage ratio of the eleventh nozzle row are not 0% or100%, and the first ink overlapping area being an area in which thenozzle usage ratio of the fifth nozzle row and the nozzle usage ratio ofthe seventh nozzle row are not 0% or 100%.
 2. The printing apparatusaccording to claim 1, wherein the sixth nozzle row and the eighth nozzlerow are configured to discharge a second ink which is neither black inknor yellow ink and is different from the first ink, the printing controlunit is configured to cause the ink to be discharged so that the firstdistance is shorter than a fourth distance, the fourth distance is adistance between a center of the first ink overlapping area and a centerof a second ink overlapping area in the first direction, the second inkoverlapping area being an area in which the nozzle usage ratio of thesixth nozzle row and the nozzle usage ratio of the eighth nozzle row arenot 0% or 100%.
 3. The printing apparatus according to claim 2, whereinthe printing control unit is configured to cause the ink to bedischarged so that the first ink overlapping area and the second inkoverlapping area at least partially prevented from overlapping with eachother when viewed from the second direction.
 4. The printing apparatusaccording to claim 3, wherein the printing control unit is configured tocause the ink to be discharged so that the first ink overlapping areaand the second ink overlapping area are prevented from overlapping witheach other when viewed from the second direction.
 5. The printingapparatus according to claim 1, wherein the printing control unit isconfigured to cause the ink to be discharged so that the black inkoverlapping area and the yellow ink overlapping area at least partiallyoverlap with each other when viewed from the second direction.
 6. Theprinting apparatus according to claim 5, wherein the printing controlunit is configured to cause the ink to be discharged so that the blackink overlapping area and the yellow ink overlapping area completelyoverlap with each other when viewed from the second direction.
 7. Aprinting method performed by a printing device including a printing headwith a plurality of nozzles for discharging ink onto a medium, theprinting head including a first printing chip, a second printing chip, athird printing chip, a fourth printing chip, a fifth printing chip, anda sixth printing chip, the first printing chip including a first nozzlerow and a second nozzle row away from each other in a second directionintersecting a first direction, the first nozzle row and the secondnozzle row including a plurality of nozzles arrayed in the firstdirection, the second printing chip including a third nozzle row and afourth nozzle row away from each other in the second direction, thethird nozzle row and the fourth nozzle row including a plurality ofnozzles arrayed in the first direction, the third printing chipincluding a fifth nozzle row and a sixth nozzle row away from each otherin the second direction, the fifth nozzle row and the sixth nozzle rowincluding a plurality of nozzles arrayed in the first direction, thefourth printing chip including a seventh nozzle row and an eighth nozzlerow away from each other in the second direction, the seventh nozzle rowand the eighth nozzle row including a plurality of nozzles arrayed inthe first direction, the fifth printing chip including a ninth nozzlerow and a tenth nozzle row away from each other in the second direction,the ninth nozzle row and the tenth nozzle row including a plurality ofnozzles arrayed in the first direction, the sixth printing chipincluding an eleventh nozzle row and a twelfth nozzle row away from eachother in the second direction, the eleventh nozzle row and the twelfthnozzle row including a plurality of nozzles arrayed in the firstdirection, the first printing chip through the sixth printing chip beingarranged to at least partially overlap with each other when viewed fromthe second direction, the first nozzle row, the third nozzle row, thetenth nozzle row, and the twelfth nozzle row discharging black ink, thesecond nozzle row, the fourth nozzle row, the ninth nozzle row, and theeleventh nozzle row discharging yellow ink of the same color, the fifthnozzle row and the seventh nozzle row discharging a first ink which isneither black ink nor yellow ink, the printing method comprising:conveying the medium relatively to the printing head; and causing theprinting head to discharge the ink onto the medium, based on a nozzleusage ratio being a ratio of the ink discharged from each of theplurality of nozzles, wherein the causing the printing head to dischargethe ink onto the medium includes causing the ink to be discharged sothat a first distance is shorter than a second distance and a thirddistance, the first distance is a distance between a center of a blackink overlapping area and a center of a yellow ink overlapping area inthe first direction, the second distance is a distance between a centerof the black ink overlapping area and a center of a first inkoverlapping area in the first direction, the third distance is adistance between a center of the yellow ink overlapping area and acenter of the first ink overlapping area in the first direction, theblack ink overlapping area being an area in which the nozzle usage ratioof the first nozzle row and the nozzle usage ratio of the third nozzlerow are not 0% or 100%, the yellow ink overlapping area being an area inwhich the nozzle usage ratio of the ninth nozzle row and the nozzleusage ratio of the eleventh nozzle row are not 0% or 100%, and the firstink overlapping area being an area in which the nozzle usage ratio ofthe fifth nozzle row and the nozzle usage ratio of the seventh nozzlerow are not 0% or 100%.